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The problems of weight loss: you may have insufficient bat: when your body can't "waste" calories

Let's tie these two subjects together. We have seen that embarking on a low-calorie diet sets in motion a chain of metabolic events, the culmination of which is a shutdown of the basal metabolic rate (BMR). As calories diminish, so does the body's ability to use them. According to some researchers, regardless of how few calories we consume, there is an inevitable 15 percent "waste factor" built in, that only about 85 percent of all ingested calories are used to meet basic energy demands or the energy required to keep the body alive and functioning. The other 15 percent of ingested calories must be dealt with.

Until recently, scientists thought the body had only one way to deal with excess calories—storage—and so fat-reducing programs were centered on just one concept: calorie restriction. It has been only in the last few years that scientists have begun to realize the importance of BAT in dealing with those excess calories in a more constructive way than simply storing them on the hips.

For normal-weight people, BAT works to eliminate the negative impact of excess calories by burning or "wasting" them in the production of body heat. Individuals who struggle with chronic weight challenges, however, may have lost the assistance of brown fat. For them, the body really does have no choice other than to store those 15 percent excess calories. For some people, especially those who cycle weight loss, their bodies have become calorie misers—energy Scrooges that desperately hang on to every calorie, packing it away into storage for another day.

"I don t feel comfortable running across the baseball field with my girls; I feel like Jurassic Park."

JANE

Genetics may also be a dominant force in the function of brown fat. Some individuals may simply be born with either inadequate amounts of BAT or their own stores of BAT are depleted for other reasons, including excessive exercise, fasting, breast-feeding, diabetes, dressing too warmly, pregnancy, fever, and hypothalamic lesions.

For others of us, the aging process or obesity begins to take its toll, and the mitochondria in brown fat begins to shut down. Reduced BAT activity can also reduce thyroid function. As the thyroid gland slows down its activity and lowers body temperature even further, a layer of white fat builds up around the internal organs, further insulating them against lower temperatures and further reducing the need for brown fat to produce heat. The downward cycle spirals faster and faster. In the process BAT is turned into WAT, becoming metabolically inactive by losing the activity of the mitochondria and shutting down the ability of the body to create heat and waste calories.

This is when, for many people, losing weight becomes an impossible dream. It simply doesn't happen, no matter how good the diet or how compliant the dieter.

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